In recent years, to enable continuous services to be provided at all times to customers, importance has been increasing for techniques regarding data replication between a plurality of storage systems so as to provide services even when failure has occurred in a storage system such as a storage device for storing data, particularly, techniques for performing data replication between remote sites and continuation/resumption for data replication in the event of failure. By way of techniques for replication information stored in a first storage system to a second storage system and a third storage system, there are techniques disclosed in a patent document described below.
In the specification of the U.S. Pat. No. 6,209,002, there is disclosed a technique in which data stored in a first storage system is transferred (replicated) to a second storage system, the transferred data is further replicated by the second storage system and transferred therefrom to a third storage system. A computer and the first storage system are connected together by means of a communication link, the first storage system and the second storage system are connected together by means of a communication link, and further, the second storage system and the third storage system are connected together by means of a communication link. The first storage system retains a replication-object first logical volume. The second storage system retains a replicated copy of the first logical volume, namely a second logical volume, and also retains a replicated copy of the second logical volume, namely a third logical volume. The third storage system retains a replicated copy of the third logical volume, namely a fourth logical volume. The second storage system exclusively executes data replication processing from the second logical volume to the third logical volume, and data replication processing from the third logical volume to the fourth logical volume.
According to the technique disclosed in the specification of the U.S. Pat. No. 6,209,002 described above, the data difference between the first logical volume and the fourth logical volume is not managed. As such, when failure has occurred in the second storage system, since the data difference is not recognized by the first storage system, the full data in the first logical volume should be transferred (replicated) to the third storage system to resume data replication in the fourth logical volume. During the data replication, a complete replicated copy regarding the first logical volume is not present, so that the time required for the processing during that time is preferably as short as possible. However, a problem is that the time is increased proportionately with the amount of the replication object data (the first logical volume).